Conventionally, technologies for promptly activating a catalyst have been developed for vehicles and the like comprising an engine in order to inhibit the discharge of harmful substances, which are generated during combustion in an engine, into the atmosphere, and for reliably inhibiting the discharge amount of such harmful substances by including a catalyst provided in an exhaust passage and capable of purifying the exhaust gas from the engine.
For example, Patent Document 1 discloses a system comprising a diesel engine and a catalyst, wherein the thermal energy of the exhaust gas flowing to the catalyst is caused to be higher than during normal operation after the diesel engine is started. With this system, the temperature of the catalyst rises to the activation temperature more promptly.
With an engine provided to a vehicle or the like, it is desirable for the engine to warm up promptly in order to promptly activate the catalyst, and in order to improve the combustion stability which will consequently lead to the improvement in the fuel consumption performance and the improvement in the exhaust gas performance. Meanwhile, with the foregoing conventional system, most of the combustion energy that is generated with the engine after the engine is started is emitted to the exhaust side as exhaust energy. Thus, the energy for warming up the engine itself becomes small, and, consequently, there is a problem in that the engine cannot be warmed up promptly.